1. Field of the Invention
This invention relates generally to electricity, conductors and insulators and more particularly to apparatus for electrically terminating a cable shield at a bulkhead adjacent an electronic equipment in a cabinet housing and limiting electromagnetic interference (EMI) radiation.
2. Description of the Prior Art
In computer equipment a central complex is located in a housing which encloses various components including a processor, power supply and an "L" module or line module having a plurality of printed circuit assemblies or cards each for supporting and interconnecting electronic circuitry. These cards function to interface processor control of the peripheral units which can include printers, disk drive, tape drive, card readers, etc. Each peripheral unit is also in a housing. Cables interconnect the cards with associated peripheral units.
Shielded, general purpose cable is usually comprised of a plurality of conductive strands wrapped by an electrically conductive shielding member such as, for example, aluminized Mylar or, preferably, braided copper. The shielding is for the purpose of limiting electromagnetic interference (EMI) radiation from the signal carrying conductors. The strands and shield are often encased in an electrically insulating wrap such as a rubberized or plasticized material. Such cables are used to transfer electrical signals between the central complex housing and each associated peripheral unit.
Within the central complex housing occurs much electronic activity often including the rapid switching of circuits. This activity produces EMI radiation within the housing. The shield of the cable picks up the EMI radiation from inside the central complex housing. If the electromagnetic signals are not discharged within the housing, the shield carries the radiation out of the housing where it is dicharged and the cables act as antennae radiating the EMI outside of the housing.
There are legally imposed limits as to how much EMI radiation is permissible, therefore, attempts have been made to comply. In order to comply, it has been found to be desirable to electrically connect the shielding to the housing, which is normally grounded. Such grounding discharges the EMI radiation as it leaves the housing. One such attempt includes using "pigtail" type connectors comprised of a section of braided shielding material electrically connected at one end to the cable shield and connected at another end to the central complex housing. These pigtail connectors have been found to be limited in their effectiveness. They are most effective when they are relatively short in length, however, it is not always convenient to work with the short pigtail type connector.
Another common practice has been to utilize a shielded connector for each cable leaving a housing, where the connector shielding is electrically coupled to the housing. Such an arrangement inhibits any EMI signals from reaching the cable shield external to the housing, but is very expensive both in parts and labor to wire the connectors.
The foregoing illustrates limitations of the known prior art. Thus, it is apparent that it would be advantageous to provide an inexpensive alternative directed to overcoming one or more of the limitations as set forth above, while providing a structure that will not damage cable shielding and will provide axial support and positioning. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.